Method and apparatus for adapting engine operation in a hybrid powertrain system for active driveline damping

ABSTRACT

A powertrain includes an engine coupled to an input member of a hybrid transmission. The hybrid transmission is operative to transfer power between an input member and a plurality of torque machines and an output member. A method for controlling the powertrain includes, monitoring operation of the hybrid transmission, determining motor torque offsets for the torque machines, transforming the motor torque offsets for the torque machines to an input torque offset and an output torque offset of the hybrid transmission, and adjusting operation of the engine based upon the input torque offset and the output torque offset of the hybrid transmission.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/985,637 filed on Nov. 5, 2007 which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure pertains to control systems for hybrid powertrainsystems.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known hybrid powertrain architectures include torque generative deviceswhich transfer torque through a transmission device to an output member.One exemplary hybrid powertrain includes a two-mode, compound-split,electromechanical transmission which utilizes an input member forreceiving tractive torque from a prime mover power source, preferably aninternal combustion engine, and an output member. The output member canbe operatively connected to a driveline for a motor vehicle fortransferring and reacting tractive torque therewith. Torque generativedevices can include internal combustion engines, fuel cells, and torquegenerating machines comprising, e.g., electric machines and hydraulicmachines. Torque generating machines can operate as torque motors totransfer torque to the transmission independently of a torque input fromthe internal combustion engine. Torque generating machines can operateas generators to transform vehicle kinetic energy transferred throughthe vehicle driveline to potential energy that is storable in anelectrical energy storage device in the form of electric power orstorable in a hydraulic accumulator energy storage device in the form ofhydraulic pressure. A control system monitors various inputs from thevehicle and the operator and provides operational control of the hybridpowertrain, including, e.g., controlling engine operation, transmissionoperating range state and gear shifting, controlling the torquegenerating machines, and regulating the power interchange among theenergy storage device and the torque generating machines to managetorque, speed, and power outputs of the transmission.

SUMMARY

A powertrain includes an engine coupled to an input member of a hybridtransmission. The hybrid transmission is operative to transfer powerbetween an input member and a plurality of torque machines and an outputmember. A method for controlling the powertrain includes, monitoringoperation of the hybrid transmission, determining motor torque offsetsfor the torque machines, transforming the motor torque offsets for thetorque machines to an input torque offset and an output torque offset ofthe hybrid transmission, and adjusting operation of the engine basedupon the input torque offset and the output torque offset of the hybridtransmission.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary hybrid powertrain, inaccordance with the present disclosure;

FIG. 2 is a schematic diagram of an exemplary architecture for a controlsystem and hybrid powertrain, in accordance with the present disclosure;and

FIGS. 3, 4, and 5 are schematic flow diagrams of a control systemarchitecture for controlling and managing torque in a hybrid powertrainsystem, in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplary hybridpowertrain. The exemplary hybrid powertrain in accordance with thepresent disclosure is depicted in FIG. 1, comprising a two-mode,compound-split, electro-mechanical hybrid transmission 10 operativelyconnected to an engine 14 and torque machines comprising first andsecond electric machines (‘MG-A’) 56 and (‘MG-B’) 72. The engine 14 andfirst and second electric machines 56 and 72 each generate mechanicalpower which can be transferred to the transmission 10. The powergenerated by the engine 14 and the first and second electric machines 56and 72 and transferred to the transmission 10 is described in terms ofinput and motor torques, referred to herein as T_(I), T_(A), and T_(B)respectively, and speed, referred to herein as N_(I), N_(A), and N_(B),respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transfer torque to thetransmission 10 via an input shaft 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input shaft 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input shaft 12. Power output from the engine 14, comprisingrotational speed and engine torque, can differ from the input speed N₁and the input torque T_(I) to the transmission 10 due to placement oftorque-consuming components on the input shaft 12 between the engine 14and the transmission 10, e.g., a hydraulic pump (not shown) and/or atorque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transferring devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit 42, preferably controlled by atransmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power to the driveline 90 that is transferred to vehiclewheels 93, one of which is shown in FIG. 1. The output power at theoutput member 64 is characterized in terms of an output rotational speedN_(O) and an output torque T_(O). A transmission output speed sensor 84monitors rotational speed and rotational direction of the output member64. Each of the vehicle wheels 93 is preferably equipped with a sensor94 adapted to monitor wheel speed, V_(SS-WHL), the output of which ismonitored by a control module of a distributed control module systemdescribed with respect to FIG. 2, to determine vehicle speed, andabsolute and relative wheel speeds for braking control, tractioncontrol, and vehicle acceleration management.

The input torque from the engine 14 and the motor torques from the firstand second electric machines 56 and 72 (T_(I), T_(A), and T_(B)respectively) are generated as a result of energy conversion from fuelor electrical potential stored in an electrical energy storage device(hereafter ‘ESD’) 74. The ESD 74 is high voltage DC-coupled to the TPIM19 via DC transfer conductors 27. The transfer conductors 27 include acontactor switch 38. When the contactor switch 38 is closed, undernormal operation, electric current can flow between the ESD 74 and theTPIM 19. When the contactor switch 38 is opened electric current flowbetween the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmitselectrical power to and from the first electric machine 56 by transferconductors 29, and the TPIM 19 similarly transmits electrical power toand from the second electric machine 72 by transfer conductors 31 tomeet the torque commands for the first and second electric machines 56and 72 in response to the motor torque commands T_(A) and T_(B).Electrical current is transmitted to and from the ESD 74 in accordancewith whether the ESD 74 is being charged or discharged.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive themotor torque commands and control inverter states therefrom forproviding motor drive or regeneration functionality to meet thecommanded motor torques T_(A) and T_(B). The power inverters compriseknown complementary three-phase power electronics devices, and eachincludes a plurality of insulated gate bipolar transistors (not shown)for converting DC power from the ESD 74 to AC power for poweringrespective ones of the first and second electric machines 56 and 72, byswitching at high frequencies. The insulated gate bipolar transistorsform a switch mode power supply configured to receive control commands.There is typically one pair of insulated gate bipolar transistors foreach phase of each of the three-phase electric machines. States of theinsulated gate bipolar transistors are controlled to provide motor drivemechanical power generation or electric power regenerationfunctionality. The three-phase inverters receive or supply DC electricpower via DC transfer conductors 27 and transform it to or fromthree-phase AC power, which is conducted to or from the first and secondelectric machines 56 and 72 for operation as motors or generators viatransfer conductors 29 and 31 respectively.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary hybrid powertrain described in FIG. 1. Thedistributed control module system synthesizes pertinent information andinputs, and executes algorithms to control various actuators to meetcontrol objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, and the TPIM 19. A hybrid control module(hereafter ‘HCP’) 5 provides supervisory control and coordination of theECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface(‘UI’) 13 is operatively connected to a plurality of devices throughwhich a vehicle operator controls or directs operation of theelectromechanical hybrid powertrain. The devices include an acceleratorpedal 113 (‘AP’), an operator brake pedal 112 (‘BP’), a transmissiongear selector 114 (‘PRNDL’), and a vehicle speed cruise control (notshown). The transmission gear selector 114 may have a discrete number ofoperator-selectable positions, including the rotational direction of theoutput member 64 to enable one of a forward and a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality including e.g., antilock braking, traction control, andvehicle stability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the hybrid powertrain, servingto coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21.Based upon various input signals from the user interface 13 and thehybrid powertrain, including the ESD 74, the HCP 5 determines anoperator torque request, an output torque command, an engine inputtorque command, clutch torque(s) for the applied torque-transferclutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, and themotor torque commands T_(A) and T_(B) for the first and second electricmachines 56 and 72.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque command from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input shaft 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters including, e.g., a manifold pressure, enginecoolant temperature, ambient air temperature, and ambient pressure. Theengine load can be determined, for example, from the manifold pressure,or alternatively, from monitoring operator input to the acceleratorpedal 113. The ECM 23 generates and communicates command signals tocontrol engine actuators, including, e.g., fuel injectors, ignitionmodules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic control circuit 42. Inputs from the TCM 17 to the HCP 5include estimated clutch torques for each of the clutches, i.e., C1 70,C2 62, C3 73, and C4 75, and rotational output speed, N_(O), of theoutput member 64. Other actuators and sensors may be used to provideadditional information from the TCM 17 to the HCP 5 for controlpurposes. The TCM 17 monitors inputs from pressure switches (not shown)and selectively actuates pressure control solenoids (not shown) andshift solenoids (not shown) of the hydraulic control circuit 42 toselectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75to achieve various transmission operating range states, as describedhereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

A brake control module (hereafter ‘BrCM’) 22 is operatively connected tofriction brakes (not shown) on each of the vehicle wheels 93. The BrCM22 monitors the operator input to the brake pedal 112 and generatescontrol signals to control the friction brakes and sends a controlsignal to the HCP 5 to operate the first and second electric machines 56and 72 based thereon.

Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM 21, and BrCM22 is preferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and SPI buses. The control algorithms are executed during preset loopcycles such that each algorithm is executed at least once each loopcycle. Algorithms stored in the non-volatile memory devices are executedby one of the central processing units to monitor inputs from thesensing devices and execute control and diagnostic routines to controloperation of the actuators, using preset calibrations. Loop cycles areexecuted at regular intervals, for example each 3.125, 6.25, 12.5, 2.5and 100 milliseconds during ongoing operation of the hybrid powertrain.Alternatively, algorithms may be executed in response to the occurrenceof an event.

The exemplary hybrid powertrain selectively operates in one of severalstates that can be described in terms of engine states comprising one ofan engine-on state (‘ON’) and an engine-off state (‘OFF’), andtransmission operating range states comprising a plurality of fixedgears and continuously variable operating modes, described withreference to Table 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode 1 C1 70 M1_Eng_On ON EVT Mode 1C1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode 1, or M1, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuously variablemode, i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 onlyto connect the shaft 60 to the carrier of the third planetary gear set28. The engine state can be one of ON (‘M2_Eng_On’) or OFF(‘M2_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O). A first fixed gear operation(‘G1’) is selected by applying clutches C1 70 and C4 75. A second fixedgear operation (‘G2’) is selected by applying clutches C1 70 and C2 62.A third fixed gear operation (‘G3’) is selected by applying clutches C262 and C4 75. A fourth fixed gear operation (‘G4’) is selected byapplying clutches C2 62 and C3 73. The fixed ratio operation ofinput-to-output speed increases with increased fixed gear operation dueto decreased gear ratios in the planetary gears 24, 26, and 28. Therotational speeds of the first and second electric machines 56 and 72,N_(A) and N_(B) respectively, are dependent on internal rotation of themechanism as defined by the clutching and are proportional to the inputspeed measured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque generative devices comprising the engine 14 and the first andsecond electric machines 56 and 72 to meet the operator torque requestat the output member 64 and transferred to the driveline 90. Based uponinput signals from the user interface 13 and the hybrid powertrainincluding the ESD 74, the HCP 5 determines the operator torque request,a commanded output torque from the transmission 10 to the driveline 90,the input torque from the engine 14, clutch torques for thetorque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission10; and the motor torques for the first and second electric machines 56and 72, respectively, as is described hereinbelow.

Final vehicle acceleration can be affected by other factors including,e.g., road load, road grade, and vehicle mass. The engine state and thetransmission operating range state are determined based upon operatingcharacteristics of the hybrid powertrain. This includes the operatortorque request communicated through the accelerator pedal 113 and brakepedal 112 to the user interface 13 as previously described. Thetransmission operating range state and the engine state may bepredicated on a hybrid powertrain torque demand caused by a command tooperate the first and second electric machines 56 and 72 in anelectrical energy generating mode or in a torque generating mode. Thetransmission operating range state and the engine state can bedetermined by an optimization algorithm or routine which determinesoptimum system efficiency based upon operator demand for power, batterystate of charge, and energy efficiencies of the engine 14 and the firstand second electric machines 56 and 72. The control system managestorque inputs from the engine 14 and the first and second electricmachines 56 and 72 based upon an outcome of the executed optimizationroutine, and system efficiencies are optimized thereby, to manage fueleconomy and battery charging. Furthermore, operation can be determinedbased upon a fault in a component or system. The HCP 5 monitors thetorque-generative devices, and determines the power output from thetransmission 10 at output member 64 that is required to meet theoperator torque request while meeting other powertrain operatingdemands, e.g., charging the ESD 74. As should be apparent from thedescription above, the ESD 74 and the first and second electric machines56 and 72 are electrically-operatively coupled for power flowtherebetween. Furthermore, the engine 14, the first and second electricmachines 56 and 72, and the electromechanical transmission 10 aremechanically-operatively coupled to transfer power therebetween togenerate a power flow to the output member 64.

FIG. 3 shows a control system architecture for controlling and managingsignal flow in a hybrid powertrain system having multiple torquegenerative devices, described hereinbelow with reference to the hybridpowertrain system of FIGS. 1 and 2, and residing in the aforementionedcontrol modules in the form of executable algorithms and calibrations.The control system architecture is applicable to alternative hybridpowertrain systems having multiple torque generative devices, including,e.g., a hybrid powertrain system having an engine and a single electricmachine, a hybrid powertrain system having an engine and multipleelectric machines. Alternatively, the hybrid powertrain system canutilize non-electric torque machines and energy storage systems, e.g.,hydraulic-mechanical hybrid transmissions using hydraulically poweredtorque machines (not shown).

In operation, the operator inputs to the accelerator pedal 113 and thebrake pedal 112 are monitored to determine the operator torque request.The operator inputs to the accelerator pedal 113 and the brake pedal 112comprise individually determinable operator torque request inputsincluding an immediate accelerator output torque request (‘Output TorqueRequest Accel Immed’), a predicted accelerator output torque request(‘Output Torque Request Accel Prdtd’), an immediate brake output torquerequest (‘Output Torque Request Brake Immed’), a predicted brake outputtorque request (‘Output Torque Request Brake Prdtd’) and an axle torqueresponse type (‘Axle Torque Response Type’). As used herein, the term‘accelerator’ refers to an operator request for forward propulsionpreferably resulting in increasing vehicle speed over the presentvehicle speed, when the operator selected position of the transmissiongear selector 114 commands operation of the vehicle in the forwarddirection. The terms ‘deceleration’ and ‘brake’ refer to an operatorrequest preferably resulting in decreasing vehicle speed from thepresent vehicle speed. The immediate accelerator output torque request,the predicted accelerator output torque request, the immediate brakeoutput torque request, the predicted brake output torque request, andthe axle torque response type are individual inputs to the controlsystem. Additionally, operation of the engine 14 and the transmission 10are monitored to determine the input speed (‘Ni’) and the output speed(‘No’).

The immediate accelerator output torque request comprises an immediatetorque request determined based upon the operator input to theaccelerator pedal 113. The control system controls the output torquefrom the hybrid powertrain system in response to the immediateaccelerator output torque request to cause positive acceleration of thevehicle. The immediate brake output torque request comprises animmediate braking request determined based upon the operator input tothe brake pedal 112. The control system controls the output torque fromthe hybrid powertrain system in response to the immediate brake outputtorque request to cause deceleration, or negative acceleration, of thevehicle. Vehicle deceleration effected by control of the output torquefrom the hybrid powertrain system is combined with vehicle decelerationeffected by a vehicle braking system (not shown) to decelerate thevehicle to achieve the immediate braking request.

The immediate accelerator output torque request is determined based upona presently occurring operator input to the accelerator pedal 113, andcomprises a request to generate an immediate output torque at the outputmember 64 preferably to accelerate the vehicle. The immediateaccelerator output torque request is unshaped, but can be shaped byevents that affect vehicle operation outside the powertrain control.Such events include vehicle level interruptions in the powertraincontrol for antilock braking, traction control and vehicle stabilitycontrol, which can be used to unshape or rate-limit the immediateaccelerator output torque request.

The predicted accelerator output torque request is determined based uponthe operator input to the accelerator pedal 113 and comprises an optimumor preferred output torque at the output member 64. The predictedaccelerator output torque request is preferably equal to the immediateaccelerator output torque request during normal operating conditions,e.g., when any one of antilock braking, traction control, or vehiclestability is not being commanded. When any one of antilock braking,traction control or vehicle stability is being commanded the predictedaccelerator output torque request remains the preferred output torquewith the immediate accelerator output torque request being decreased inresponse to output torque commands related to the antilock braking,traction control, or vehicle stability control.

The immediate brake output torque request is determined based upon theoperator input to the brake pedal 112 and the control signal to controlthe friction brakes to generate friction braking torque.

The predicted brake output torque request comprises an optimum orpreferred brake output torque at the output member 64 in response to anoperator input to the brake pedal 112 subject to a maximum brake outputtorque generated at the output member 64 allowable regardless of theoperator input to the brake pedal 112. In one embodiment the maximumbrake output torque generated at the output member 64 is limited to −0.2g. The predicted brake output torque request can be phased out to zerowhen vehicle speed approaches zero regardless of the operator input tothe brake pedal 112. As desired by a user, there can be operatingconditions under which the predicted brake output torque request is setto zero, e.g., when the operator setting to the transmission gearselector 114 is set to a reverse gear, and when a transfer case (notshown) is set to a four-wheel drive low range. The operating conditionswhereat the predicted brake output torque request is set to zero arethose in which blended braking is not preferred due to vehicle operatingfactors.

The axle torque response type comprises an input state for shaping andrate-limiting the output torque response through the first and secondelectric machines 56 and 72. The input state for the axle torqueresponse type can be an active state, preferably comprising one of apleasability limited state a maximum range state, and an inactive state.When the commanded axle torque response type is the active state, theoutput torque command is the immediate output torque. Preferably thetorque response for this response type is as fast as possible.

Blended brake torque includes a combination of the friction brakingtorque generated at the wheels 93 and the output torque generated at theoutput member 64 which reacts with the driveline 90 to decelerate thevehicle in response to the operator input to the brake pedal 112. TheBrCM 22 commands the friction brakes on the wheels 93 to apply brakingforce and generates a command for the transmission 10 to create anegative output torque which reacts with the driveline 90 in response tothe immediate braking request. Preferably the applied braking force andthe negative output torque can decelerate and stop the vehicle so longas they are sufficient to overcome vehicle kinetic power at wheel(s) 93.The negative output torque reacts with the driveline 90, thustransferring torque to the electromechanical transmission 10 and theengine 14. The negative output torque reacted through theelectromechanical transmission 10 can be transferred to the first andsecond electric machines 56 and 72 to generate electric power forstorage in the ESD 74.

A strategic optimization control scheme (‘Strategic Control’) 310determines a preferred input speed (‘Ni_Des’) and a preferred enginestate and transmission operating range state (‘Hybrid Range State Des’)based upon the output speed and the operator torque request and basedupon other operating parameters of the hybrid powertrain, includingbattery power limits and response limits of the engine 14, thetransmission 10, and the first and second electric machines 56 and 72.The predicted accelerator output torque request and the predicted brakeoutput torque request are input to the strategic optimization controlscheme 310. The strategic optimization control scheme 310 is preferablyexecuted by the HCP 5 during each 100 ms loop cycle and each 25 ms loopcycle. The desired operating range state for the transmission 10 and thedesired input speed from the engine 14 to the transmission 10 are inputsto the shift execution and engine start/stop control scheme 320.

The shift execution and engine start/stop control scheme 320 commandschanges in the transmission operation (‘Transmission Commands’)including changing the operating range state based upon the inputs andoperation of the powertrain system. This includes commanding executionof a change in the transmission operating range state if the preferredoperating range state is different from the present operating rangestate by commanding changes in application of one or more of theclutches C1 70, C2 62, C3 73, and C4 75 and other transmission commands.The present operating range state (‘Hybrid Range State Actual’) and aninput speed profile (‘Ni_Prof’) can be determined. The input speedprofile is an estimate of an upcoming input speed and preferablycomprises a scalar parametric value that is a targeted input speed forthe forthcoming loop cycle. The input speed profile is useful duringtransmission shifting, in order to determine a target engine speed toachieve an input speed that effect synchronous clutch speed to minimizeclutch slippage.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine 14,including a preferred input torque from the engine 14 to thetransmission 10 based upon the output speed, the input speed, and theoperator torque request comprising the immediate accelerator outputtorque request, the predicted accelerator output torque request, theimmediate brake output torque request, the predicted brake output torquerequest, the axle torque response type, and the present operating rangestate for the transmission. The engine commands also include enginestates including one of an all-cylinder operating state and a cylinderdeactivation operating state wherein a portion of the engine cylindersare deactivated and unfueled, and engine states including one of afueled state and a fuel cutoff state. An engine command comprising thepreferred input torque of the engine 14 and a present input torque(‘Ti’) reacting between the engine 14 and the input member 12 arepreferably determined in the ECM 23. Clutch torques (‘Tcl’) for each ofthe clutches C1 70, C2 62, C3 73, and C4 75, including the presentlyapplied clutches and the non-applied clutches are estimated, preferablyin the TCM 17.

An output and motor torque determination scheme (‘Output and MotorTorque Determination’) 340 is executed to achieve the preferred outputtorque from the powertrain (‘To_cmd’). This includes determining motortorque commands (‘T_(A)’, ‘T_(B)’) to transfer a net commanded outputtorque to the output member 64 of the transmission 10 that meets theoperator torque request, by controlling the first and second electricmachines 56 and 72 in this embodiment. The immediate accelerator outputtorque request, the immediate brake output torque request, the presentinput torque from the engine 14 and the estimated applied clutchtorque(s), the present operating range state of the transmission 10, theinput speed, the input speed profile, and the axle torque response typeare inputs. The output and motor torque determination scheme 340executes to determine the motor torque commands during each iteration ofone of the loop cycles. The output and motor torque determination scheme340 includes algorithmic code which is regularly executed during the6.25 ms and 12.5 ms loop cycles to determine the preferred motor torquecommands.

The hybrid powertrain is controlled to transfer the output torque to theoutput member 64 to react with the driveline 90 to generate tractivetorque at wheel(s) 93 to forwardly propel the vehicle in response to theoperator input to the accelerator pedal 113 when the operator selectedposition of the transmission gear selector 114 commands operation of thevehicle in the forward direction. Similarly, the hybrid powertrain iscontrolled to transfer the output torque to the output member 64 toreact with the driveline 90 to generate tractive torque at wheel(s) 93to propel the vehicle in a reverse direction in response to the operatorinput to the accelerator pedal 113 when the operator selected positionof the transmission gear selector 114 commands operation of the vehiclein the reverse direction. Preferably, propelling the vehicle results invehicle acceleration so long as the output torque is sufficient toovercome external loads on the vehicle, e.g., due to road grade,aerodynamic loads, and other loads.

FIG. 5 details signal flow for the output and motor torque determinationscheme 340 for controlling and managing the output torque through thefirst and second electric machines 56 and 72, described with referenceto the hybrid powertrain system of FIGS. 1 and 2 and the control systemarchitecture of FIG. 3. The output and motor torque determination scheme340 controls the motor torque commands of the first and second electricmachines 56 and 72 to transfer a net output torque to the output member64 of the transmission 10 that reacts with the driveline 90 and meetsthe operator torque request, subject to constraints and shaping. Theoutput and motor torque determination scheme 340 preferably includesalgorithmic code and predetermined calibration code which is regularlyexecuted during the 6.25 ms and 12.5 ms loop cycles to determinepreferred motor torque commands (‘T_(A)’, ‘T_(B)’) for controlling thefirst and second electric machines 56 and 72 in this embodiment.

The output and motor torque determination scheme 340 determines and usesa plurality of inputs to determine constraints on the output torque,from which it determines the output torque command (‘To_cmd’). The motortorque commands (‘T_(A)’, ‘T_(B)’) for the first and second electricmachines 56 and 72 can be determined based upon the output torquecommand. The inputs to the output and motor torque determination scheme340 include operator inputs, powertrain system inputs and constraints,and autonomic control inputs.

The operator inputs include the immediate accelerator output torquerequest (‘Output Torque Request Accel Immed’) and the immediate brakeoutput torque request (‘Output Torque Request Brake Immed’).

The autonomic control inputs include motor torque offsets to effectactive damping of the driveline 90 (412), to effect engine pulsecancellation (408), and to effect a closed loop correction based uponthe input and clutch slip speeds (410). The motor torque offsets for thefirst and second electric machines 56 and 72 to effect active damping ofthe driveline 90 can be determined (‘Ta AD’, ‘Tb AD’), e.g., to manageand effect driveline lash adjustment, and are output from an activedamping algorithm (‘AD’) (412). The active damping comprises adjustmentsto the motor torques to maintain minimum torque on components of thedriveline 90 at low speed and low torque operating conditions to preventdriveline clunk. The motor torque offsets to effect engine pulsecancellation (‘Ta PC’, ‘Tb PC’) are determined during starting andstopping of the engine during transitions between the engine-on state(‘ON’) and the engine-off state (‘OFF’) to cancel engine torquedisturbances, and are output from a pulse cancellation algorithm (‘PC’)(408).

The motor torque offsets for the first and second electric machines 56and 72 to effect closed-loop correction torque are determined bymonitoring input speed to the transmission 10 and clutch slip speeds ofclutches C1 70, C2 62, C3 73, and C4 75. The closed-loop correctionmotor torque offsets for the first and second electric machines 56 and72 (‘Ta CL’, ‘Tb CL’) can be determined based upon an input speed error,i.e., a difference between the input speed from sensor 11 (‘Ni’) and theinput speed profile (‘Ni_Prof’), and a clutch slip speed error, i.e., adifference between clutch slip speed and a targeted clutch slip speed,e.g., a clutch slip speed profile for a targeted clutch C1 70. Whenoperating in one of the mode operating range states, the closed-loopcorrection motor torque offsets for the first and second electricmachines 56 and 72 (‘Ta CL’, ‘Tb CL’) can be determined primarily basedupon the input speed error. When operating in Neutral, the closed-loopcorrection is based upon the input speed error and the clutch slip speederror for a targeted clutch, e.g., C1 70. The closed-loop correctionmotor torque offsets are output from a closed loop control algorithm(‘CL’) (410). The clutch slip speeds of the non-applied clutches can bedetermined for the specific operating range state based upon motorspeeds for the first and second electric machines 56 and 72 and thespeed of the output member 64. The targeted clutch slip speed and clutchslip profile are preferably used during a transition in the operatingrange state of the transmission to synchronize clutch slip speed priorto applying an oncoming clutch. The closed-loop motor torque offsets andthe motor torque offsets to effect active damping of the driveline 90are input to a low pass filter (‘LPF’) 405 to determine filtered motortorque corrections for the first and second electric machines 56 and 72(‘Ta LPF’ and Tb LPF’).

The motor torque offsets for the first and second electric machines 56and 72 are converted to a corresponding input torque offset T_(I) CL andan output torque offset T_(O) CL using a linear transformation (‘PMap toTi, To’) (406). The linear transformation comprises a transformationfrom the motor torques, e.g., the filtered motor torque corrections forthe first and second electric machines 56 and 72 (‘Ta LPF’ and Tb LPF’),to a corresponding input torque T_(I) and output torque T_(O). Therelationship between the motor torques and the input and output torqueis set forth below:

$\begin{matrix}{\begin{bmatrix}{T_{I}{CL}} \\{T_{O}{CL}}\end{bmatrix} = {\begin{bmatrix}{a\; 11} & {a\; 12} \\{a\; 21} & {a\; 22}\end{bmatrix} \cdot \begin{bmatrix}{T_{a}L\; P\; F} \\{T_{b}L\; P\; F}\end{bmatrix}}} & \lbrack 1\rbrack\end{matrix}$wherein the terms a11, a12, a21, a22 are based upon a physicalrelationship between elements of the transmission 14 to transfer powerbetween the input member 12 and the output member 64 includingindependently controllable elements including the motor torques andinput and output speeds of the transmission 14 and dependent upon theoperating range state of the transmission 14.

The relationship of Eq. 1 is expressed in Eqs. 2 and 3 and calibratedand reduced to algorithmic code for execution preferably in the HCP 5.When the transmission 14 is in one of the fixed gear operating rangestates, the linear transformation is set forth below:

$\begin{matrix}{{T_{a}L\; P\; F} = {\begin{bmatrix}{b\; 1} & {b\; 2} & {b\; 3} & {b\; 4}\end{bmatrix}\begin{bmatrix}{T_{I}{CL}} \\{T_{a}L\; P\; F} \\{T_{O}{CL}} \\\overset{.}{N_{I}}\end{bmatrix}}} & \lbrack 2\rbrack\end{matrix}$wherein b1-b4 are calibratable scalar values, as described withreference to a11-a22, and {dot over (N)}₁ is a time-rate change in theinput speed of the input member 12.

When the transmission 14 is in one of the mode operating range states,the torque converter map is set forth below:

$\begin{matrix}{\begin{bmatrix}{T_{a}L\; P\; F} \\{T_{b}L\; P\; F}\end{bmatrix} = {\begin{bmatrix}{c\; 11} & {c\; 12} & {c\; 13} & {c\; 14} \\{c\; 21} & {c\; 22} & {c\; 23} & {c\; 24}\end{bmatrix}\begin{bmatrix}{T_{I}{CL}} \\{T_{O}{CL}} \\{\overset{.}{N}}_{I} \\\overset{.}{N_{O}}\end{bmatrix}}} & \lbrack 3\rbrack\end{matrix}$wherein a11-a24 are calibratable scalar values, and {dot over (N)}_(O)is a time-rate change in the output speed. Thus, the total motor torqueoffsets for the first and second electric machines 56 and 72 due toengine input power can be linearly transformed to the input and outputtorque offsets T_(I)CL and T_(O)CL that are input to the tacticalcontrol scheme 330.

Other aspects of the output and motor torque determination scheme 340are now described. Inputs including an input acceleration profile(‘Nidot_Prof’) and a clutch slip acceleration profile (“Clutch SlipAccel Prof’) are input to a pre-optimization algorithm (415), along withthe system inputs, the operating range state, and the motor torquecorrections for the first and second electric machines 56 and 72 (‘TaLPF’ and ‘Tb LPF’). The input acceleration profile is an estimate of anupcoming input acceleration that preferably comprises a targeted inputacceleration for the forthcoming loop cycle. The clutch slipacceleration profile is an estimate of upcoming clutch acceleration forone or more of the non-applied clutches, and preferably comprises atargeted clutch slip acceleration for the forthcoming loop cycle.Optimization inputs (‘Opt Inputs’), which can include values for motortorques, clutch torques and output torques can be calculated for thepresent operating range state and used in an optimization algorithm(440). The optimization algorithm (440) is preferably executed todetermine the maximum and minimum raw output torque constraints (440)and to determine the preferred split of open-loop torque commandsbetween the first and second electric machines 56 and 72 (440′). Theoptimization inputs, the maximum and minimum battery power limits, thesystem inputs and the present operating range state are analyzed todetermine a preferred or optimum output torque (‘To Opt’) and minimumand maximum raw output torque constraints (‘To Min Raw’, ‘To Max Raw’)which can be shaped and filtered (420). The preferred output torque (‘ToOpt’) comprises an output torque that minimizes battery power subject toa range of net output torques that are less than the immediateaccelerator output torque request. The preferred output torque comprisesthe net output torque that is less than the immediate accelerator outputtorque request and yields the minimum battery power subject to theoutput torque constraints. The immediate accelerator output torquerequest and the immediate brake output torque request are each shapedand filtered and subjected to the minimum and maximum output torqueconstraints (‘To Min Filt’, ‘To Max Filt’) to determine minimum andmaximum filtered output torque request constraints (‘To Min Req Filt’,‘To Max Req Filt’). A constrained accelerator output torque request (‘ToReq Accel Cnstrnd’) and a constrained brake output torque request (‘ToReq Brake Cnstrnd’) can be determined based upon the minimum and maximumfiltered output torque request constraints (425).

Furthermore, a regenerative braking capacity (‘Opt Regen Capacity’) ofthe transmission 10 comprises a capacity of the transmission 10 to reactdriveline torque, and can be determined based upon constraints includingmaximum and minimum motor torque outputs from the torque machines andmaximum and minimum reactive torques for the applied clutches, takinginto account the battery power limits. The regenerative braking capacityestablishes a maximum value for the immediate brake output torquerequest. The regenerative braking capacity is determined based upon adifference between the constrained accelerator output torque request andthe preferred output torque (‘To Opt’). The constrained acceleratoroutput torque request is shaped and filtered and combined with aconstrained, shaped, and filtered brake output torque request todetermine a net output torque command. The net output torque command iscompared to the minimum and maximum request filtered output torques todetermine the output torque command (‘To_cmd’) (430). When the netoutput torque command is between the maximum and minimum requestfiltered output torques, the output torque command is set to the netoutput torque command. When the net output torque command exceeds themaximum request filtered output torque, the output torque command is setto the maximum request filtered output torque. When the net outputtorque command is less than the minimum request filtered output torque,the output torque command is set to the minimum request filtered outputtorque command.

Powertrain operation is monitored and combined with the output torquecommand to determine a preferred split of open-loop torque commandsbetween the first and second electric machines 56 and 72 that meetsreactive clutch torque capacities (‘Ta Opt’ and ‘Tb Opt’), and providefeedback related to the preferred battery power (‘Pbat Opt’) (440′). Themotor torque corrections for the first and second electric machines 56and 72 (‘Ta LPF’ and Tb LPF’) are subtracted to determine open loopmotor torque commands (‘Ta OL’ and ‘Tb OL’) (460).

The open loop motor torque commands are combined with the autonomiccontrol inputs including the motor torque offsets to effect activedamping of the driveline 90 (412), to effect engine pulse cancellation(408), and to effect a closed loop correction based upon the input andclutch slip speeds (410), to determine the motor torques T_(A) and T_(B)for controlling the first and second electric machines 56 and 72 (470).The aforementioned steps of constraining, shaping and filtering theoutput torque request to determine the output torque command which isconverted into the torque commands for the first and second electricmachines 56 and 72 is preferably a feed-forward operation which actsupon the inputs and uses algorithmic code to calculate the torquecommands.

The system operation as configured leads to determining output torqueconstraints based upon present operation and constraints of thepowertrain system. The operator torque request is determined based uponoperator inputs to the brake pedal and to the accelerator pedal. Theoperator torque request can be constrained, shaped and filtered todetermine the output torque command, including determining a preferredregenerative braking capacity. An output torque command can bedetermined that is constrained based upon the constraints and theoperator torque request. The output torque command is implemented bycommanding operation of the torque machines. The system operationeffects powertrain operation that is responsive to the operator torquerequest and within system constraints. The system operation results inan output torque shaped with reference to operator drivability demands,including smooth operation during regenerative braking operation.

The optimization algorithm (440, 440′) comprises an algorithm executedto determine powertrain system control parameters that are responsive tothe operator torque request that minimizes battery power consumption.The optimization algorithm (440, 440′) includes monitoring presentoperating conditions of the electromechanical hybrid powertrain, e.g.,the powertrain system described hereinabove, based upon the systeminputs and constraints, the present operating range state, and theavailable battery power limits. For a candidate input torque, theoptimization algorithm (440, 440′) calculates powertrain system outputsthat are responsive to the system inputs comprising the aforementionedoutput torque commands and are within the maximum and minimum motortorque outputs from the first and second electric machines 56 and 72,and within the available battery power, and within the range of clutchreactive torques from the applied clutches for the present operatingrange state of the transmission 10, and take into account the systeminertias, damping, clutch slippages, and electric/mechanical powerconversion efficiencies. Preferably, the powertrain system outputsinclude the preferred output torque (‘To Opt’), achievable torqueoutputs from the first and second electric machines 56 and 72 (‘Ta Opt’,‘Tb Opt’) and the preferred battery power (‘Pbat Opt’) associated withthe achievable torque outputs.

The constraints on the output torque request (440) comprising maximumand minimum unfiltered output torques are determined based upon inputsincluding the input speed, output speed, motor torque constraints,reactive clutch torque constraints for the applied clutches, and inputand output accelerations. The preferred output torque is subject to theoutput torque constraints and is determined based upon the range ofallowable output torques, which can vary, and may include the immediateaccelerator output torque request. The preferred output torque maycomprise an output torque corresponding to a minimum battery dischargepower or an output torque corresponding to a maximum battery chargepower. The preferred output torque is based upon a capacity of thepowertrain to transmit and convert electric power to mechanical torquethrough the first and second electric machines 56 and 72, and theimmediate or present torque, speed, and reactive clutch torqueconstraints, and electric power inputs thereto. During ongoingoperation, the control system uses the control schemes to control thepowertrain system described herein by determining and adapting the inputtorque from the engine 14 and the engine state using feed-forwardcontrol. The operator inputs to the accelerator pedal and the brakepedal are monitored to determine the output torque request, or theoperator torque request.

FIG. 4 details the tactical control scheme (‘Tactical Control andOperation’) 330 for controlling operation of the engine 14, describedwith reference to the hybrid powertrain system of FIGS. 1 and 2 and thecontrol system architecture of FIG. 3. The tactical control scheme 330includes a tactical optimization control path 350 and a systemconstraints control path 360 which are preferably executed concurrently.The outputs of the tactical optimization control path 350 are input toan engine state control scheme 370. The outputs of the engine statecontrol scheme 370 and the system constraints control path 360 are inputto an engine response type determination scheme (‘Engine Response TypeDetermination’) 380 for controlling the engine state, the immediateengine torque request and the predicted engine torque request.

The operating point of the engine 14 as described in terms of the inputtorque and input speed that can be achieved by controlling mass ofintake air to the engine 14 when the engine 14 comprises aspark-ignition engine by controlling position of an engine throttle (notshown) utilizing an electronic throttle control device (not shown). Thisincludes opening the throttle to increase the engine input speed andtorque output and closing the throttle to decrease the engine inputspeed and torque. The engine operating point can be achieved byadjusting ignition timing, generally by retarding spark timing from amean-best-torque spark timing to decrease engine torque.

When the engine 14 comprises a compression-ignition engine, theoperating point of the engine 14 can be achieved by controlling the massof injected fuel, and adjusted by retarding injection timing from amean-best-torque injection timing to decrease engine torque.

The engine operating point can be achieved by changing the engine statebetween the engine-off state and the engine-on state. The engineoperating point can be achieved by controlling the engine state betweenthe all-cylinder state and the cylinder deactivation state, wherein aportion of the engine cylinders are unfueled and the engine valves aredeactivated. The engine state can include the fuel cutoff state whereinthe engine is rotating and unfueled to effect engine braking.

The input and output torque offsets T_(I) CL and T_(O) CL are input to alow pass filter 335 of the tactical control scheme 330, yieldingfiltered input and output torque offsets T_(I) CL Filt and T_(O) CL Filtthat are input to the tactical optimization control path 350 and to thesystem constraints control path 360.

The tactical optimization control path 350 acts on substantiallysteady-state inputs to select a preferred engine state and determine apreferred input torque from the engine 14 to the transmission 10. Thetactical optimization control path 350 includes an optimization scheme(‘Tactical Optimization’) 354 to determine preferred input torques foroperating the engine 14 in the all-cylinder state (‘Input Torque Full’),in the cylinder deactivation state (‘Input Torque Deac’), theall-cylinder state with fuel cutoff (‘Input Torque Full FCO’), in thecylinder deactivation state with fuel cutoff (‘Input Torque Deac FCO’),and a preferred engine state (‘Engine State’).

Inputs to the optimization scheme 354 include the filtered input andoutput torque offsets T_(I)CL Filt and T_(O)CL Filt, a lead operatingrange state of the transmission 10 (‘Lead Hybrid Range State’) a leadpredicted input acceleration profile (‘Lead Input Acceleration ProfilePredicted’), a predicted range of clutch reactive torques (‘PredictedClutch Reactive Torque Min/Max’) across each applied clutch in the leadoperating range state, and predicted battery power limits (‘PredictedBattery Power Limits’).

The predicted output torque requests for acceleration and braking arecombined and shaped with the axle torque response type through apredicted output torque shaping filter 352 to yield a net predictedoutput torque (‘To Net Prdtd’) and a predicted accelerator output torque(‘To Accel Prdtd’), which are inputs to the optimization scheme 354, andadjusted with the filtered output torque offset T_(O)CL Filt. The leadoperating range state of the transmission 10 comprises a time-shiftedlead of the operating range state of the transmission 10 to accommodatea response time lag between a commanded change in the operating rangestate and the actual operating range state. Thus the lead operatingrange state of the transmission 10 is the commanded operating rangestate. The lead predicted input acceleration profile comprises atime-shifted lead of the predicted input acceleration profile of theinput member 12 to accommodate a response time lag between a commandedchange in the predicted input acceleration profile and a measured changein the predicted input acceleration profile. Thus the lead predictedinput acceleration profile is the predicted input acceleration profileof the input member 12 occurring after the time shift. The parametersdesignated as ‘lead’ are used to accommodate concurrent transfer oftorque through the powertrain converging at the common output member 64using devices having varying response times. Specifically, the engine 14can have a response time of an order of magnitude of 300-600 ms, andeach of the torque transfer clutches C1 70, C2 62, C3 73, and C4 75 canhave response times of an order of magnitude of 150-300 ms, and thefirst and second electric machines 56 and 72 can have response time ofan order of magnitude of 10 ms.

The optimization scheme 354 determines costs for operating the engine 14in each of the engine states, which comprise operating the engine fueledand in the all-cylinder state (‘P_(COST FULL FUEL)’), operating theengine unfueled and in the all-cylinder state (‘P_(COST FULL FCO)’),operating the engine fueled and in cylinder deactivation state(‘P_(COST DEAC FUEL)’), and operating the engine unfueled and in thecylinder deactivation state (‘P_(COST DEAC FCO)’). The aforementionedcosts for operating the engine 14 are input to a stabilization analysisscheme (‘Stabilization and Arbitration’) 356 along with the actualengine state (‘Actual Engine State’) and an allowable or permissibleengine state (‘Engine State Allowed’) to select one of the engine statesas the preferred engine state (‘Optimal Engine State’).

The preferred input torques for operating the engine 14 in theall-cylinder state and in the cylinder deactivation state with andwithout fuel cutoff are input to an engine torque conversion calculator355 and converted to preferred engine torques in the all-cylinder stateand in the cylinder deactivation state (‘Optimal Engine Torque Full’)and (‘Optimal Engine Torque Deac’) and with fuel cutoff in theall-cylinder state and in the cylinder deactivation state (‘EngineTorque Full FCO’) and (‘Engine Torque Deac FCO’) respectively, by takinginto account parasitic and other loads introduced between the engine 14and the transmission 10. The preferred engine torques and the preferredengine state comprise inputs to the engine state control scheme 370.

The costs for operating the engine 14 include operating costs which aredetermined based upon factors that include vehicle drivability, fueleconomy, emissions, and battery usage. Costs are assigned and associatedwith fuel and electrical power consumption and are associated with aspecific operating points of the hybrid powertrain. Lower operatingcosts can be associated with lower fuel consumption at high conversionefficiencies, lower battery power usage, and lower emissions for eachengine speed/load operating point, and take into account the presentoperating state of the engine 14.

The preferred engine state and the preferred engine torques are input tothe engine state control scheme 370, which includes an engine statemachine (‘Engine State Machine’) 372. The engine state machine 372determines a target engine torque (‘Target Engine Torque’) and an enginestate (‘Engine State’) based upon the preferred engine torques and thepreferred engine state. The target engine torque and the target enginestate are input to a transition filter 374 which monitors any commandedtransition in the engine state and filters the target engine torque toprovide a filtered target engine torque (‘Filtered Target EngineTorque’). The engine state machine 372 outputs a command that indicatesselection of one of the cylinder deactivation state and the all-cylinderstate (‘DEAC Selected’) and indicates selection of one of theengine-fueled state and the deceleration fuel cutoff state (‘FCOSelected’). The selection of one of the cylinder deactivation state andthe all-cylinder state and the selection of one of the engine-fueledstate and the deceleration fuel cutoff state, the filtered target enginetorque, and the minimum and maximum engine torques are input to theengine response type determination scheme 380.

The system constraints control path 360 determines constraints on theinput torque, comprising minimum and maximum input torques (‘InputTorque Hybrid Minimum’ and ‘Input Torque Hybrid Maximum’) that can bereacted by the transmission 10. The minimum and maximum input torquesare determined based upon constraints to the transmission 10 and thefirst and second electric machines 56 and 72, including clutch torquesand battery power limits, which affect the capacity of the transmission10 to react input torque during the current loop cycle. Inputs to thesystem constraints control path 360 include the immediate output torquerequest as measured by the accelerator pedal 113 (‘Output Torque RequestAccel Immed’) and the immediate output torque request as measured by thebrake pedal 112 (‘Output Torque Request Brake Immed’) which are combinedand shaped with the axle torque response type through an immediateoutput torque shaping filter 362 to yield a net immediate output torque(‘To Net Immed’) and an immediate accelerator output torque (‘To AccelImmed’). The net immediate output torque and the immediate acceleratoroutput torque are inputs to a constraints scheme (‘Output and InputTorque Constraints’) 364. Other inputs to the constraints scheme 364include the lead operating range state of the transmission 10, animmediate lead input acceleration profile (‘Lead Input AccelerationProfile Immed’), a lead immediate clutch reactive torque range (‘LeadImmediate Clutch Reactive Torque Min/Max’) for each applied clutch inthe lead operating range state, and the available battery power(‘Battery Power Limits’) comprising the range P_(BAT) _(—) _(MIN) toP_(BAT) _(—) _(MAX). The filtered input and output torque offsetsT_(I)CL Filt and T_(O)CL Filt are also inputs.

A targeted lead input acceleration profile comprises a time-shifted leadof the immediate input acceleration profile of the input member 12 toaccommodate a response time lag between a commanded change in theimmediate input acceleration profile and a measured change in theimmediate input acceleration profile. The lead immediate clutch reactivetorque range comprises a time-shifted lead of the immediate clutchreactive torque range of the clutches to accommodate a response time lagbetween a commanded change in the immediate clutch torque range and ameasured change in the immediate clutch reactive torque range. Theconstraints scheme 364 determines an output torque range for thetransmission 10 comprising maximum and minimum output torques that areachievable based upon constraints imposed by the system operation asdescribed, including the output torque offsets T_(I)CL Filt and T_(O)CLFilt. The constraints scheme 364 then determines the minimum and maximuminput torques that can be reacted by the transmission 10 based upon theaforementioned inputs and the output torque range for the transmission10 comprising the maximum and minimum achievable output torques.

The minimum and maximum input torques are input to the engine torqueconversion calculator 355 and converted to minimum and maximum enginetorques (‘Engine Torque Hybrid Minimum’ and ‘Engine Torque HybridMaximum’ respectively), by taking into account parasitic and other loadsintroduced between the engine 14 and the transmission 10.

The filtered target engine torque, the output of the engine statemachine 372 and the engine minimum and maximum engine torques are inputto the engine response type determination scheme 3 80, which inputs theengine commands to the ECM 23 for controlling the engine state, theimmediate engine torque request and the predicted engine torque request.The engine commands include an immediate engine torque request (‘EngineTorque Request Immed’) and a predicted engine torque request (‘EngineTorque Request Prdtd’) that can be determined based upon the filteredtarget engine torque. Other commands control the engine state to one ofthe engine fueled state and the deceleration fuel cutoff state (‘FCORequest’) and to one of the cylinder deactivation state and theall-cylinder state (‘DEAC Request’). Another output comprises an engineresponse type (‘Engine Response Type’). When the filtered target enginetorque is within the range between the minimum and maximum enginetorques, the engine response type is inactive. When the filtered targetengine torque is outside the constraints of the minimum and maximumengine torques (‘Engine Torque Hybrid Minimum’) and (‘Engine TorqueHybrid Maximum’) the engine response type is active, indicating a needfor an immediate change in the engine torque, e.g., through engine sparkcontrol and retard to change the engine torque and the input torque tofall within the constraints of the minimum and maximum engine torques.

The operating system as described commands input torque from the engineand motor torques from the first and second electric machines 56 and 72to achieve the preferred output torque in response to the operatortorque request. When there is an error in the input torque from theengine 14 to the hybrid transmission 10, the output and motor torquedetermination scheme 340 executes to achieve the preferred outputtorque, including adjusting motor torque commands for the first andsecond electric machines 56 and 72, which can result in excessivecharging or discharging of the ESD 74. Errors in the input torque fromthe engine 14 can be based upon incorrect engine input torque estimatesand errors in mechanical spin losses. Thus, the system as described canbe used to determine errors in the input from the engine, as evidencedby errors in the input speed and errors in clutch slip speed, and canadjust operation of the engine 14 to minimize and eliminate excessivecharging or discharging of the ESD 74. Adjusting operation of the engine14 includes changing the engine operation to change input torque fromthe engine 14 to the transmission 10, changing the engine state tochange engine operating efficiency, and changing constraints on theengine operation to effect changes in the engine state and the engineoperating point and forestall excessive charging or discharging of theESD 74.

It is understood that modifications are allowable within the scope ofthe disclosure. The disclosure has been described with specificreference to the preferred embodiments and modifications thereto.Further modifications and alterations may occur to others upon readingand understanding the specification. It is intended to include all suchmodifications and alterations insofar as they come within the scope ofthe disclosure.

1. Method for controlling a powertrain comprising an engine coupled toan input member of a hybrid transmission, the hybrid transmissionoperative to transfer power between the input member and a plurality oftorque machines and an output member, the method comprising: monitoringoperation of the hybrid transmission; determining motor torque offsetsfor the torque machines, said motor torque offsets for the torquemachines comprising closed-loop motor torque offsets effectingclosed-loop correction torque based upon an input speed error of theinput member and motor torque offsets effecting active damping of adriveline operatively connected to the output member, said input speederror comprising a difference between a measured input speed of theinput member provided by the engine and an input speed profilecomprising an estimate of an upcoming input speed; transforming themotor torque offsets for the torque machines to an input torque offsetand an output torque offset of the hybrid transmission, saidtransforming comprising a linear transformation based on a time rate ofchange in an input speed of the input member provided by the engine; andadjusting operation of the engine based upon the input torque offset andthe output torque offset of the hybrid transmission.
 2. The method ofclaim 1, further comprising determining the motor torque offsets for thetorque machines based upon the input speed error of the input memberwhen operating the hybrid transmission in a continuously variableoperating range state.
 3. The method of claim 1, further comprisingdetermining the motor torque offsets for the torque machines based uponthe input speed error of the input member and a clutch slip speed errorwhen operating the hybrid transmission in a neutral mode.
 4. The methodof claim 1, further comprising adjusting a preferred input torque fromthe engine to the input member based upon the input torque offset andthe output torque offset of the hybrid transmission.
 5. The method ofclaim 4, further comprising adjusting a preferred engine state basedupon the input torque offset and the output torque offset of the hybridtransmission.
 6. The method of claim 1, comprising adjusting inputtorque constraints to the hybrid transmission based upon the inputtorque offset and the output torque offset of the hybrid transmission.7. Method for controlling a powertrain system including an enginecoupled to an input member of a transmission and a plurality of torquemachines connected to an energy storage device, the transmissionoperative to transfer power between the engine and the torque machinesand an output member coupled to a driveline through selective actuationof a plurality of torque transfer clutches, the method comprising:monitoring operator inputs to an accelerator pedal and to a brake pedal;determining an output torque request based upon the operator inputs tothe accelerator pedal and to the brake pedal; monitoring an input speedof the input member of transmission provided by the engine; determininga clutch slip speed for one of the torque transfer clutches; determininga target input speed and a target clutch slip speed; determining motortorque offsets for the torque machines comprising closed-loop motortorque offsets effecting closed-loop correction torque based upon adifference between the input speed provided by the engine and thetargeted input speed, a difference between the clutch slip speed and thetarget clutch slip speed, and motor torque offsets effecting activedamping of a driveline operatively connected to the output member;transforming the motor torque offsets for the torque generating machinesto an input torque offset and a output torque offset to thetransmission, said transforming comprising a linear transformation basedon a time rate of change in the input speed of the input member providedby the engine; and adjusting the input torque from the engine to thetransmission and selecting a preferred engine state based upon the inputtorque offset and the output torque offset to the transmission. 8.Method for controlling a powertrain system including a hybridtransmission operative to transfer power between an engine, torquemachines, an energy storage device, and an output member, the methodcomprising: determining an output torque command; monitoring an inputparameter from the engine to the transmission; determining a targetstate for the input parameter from the engine; determining motor torqueoffsets for the torque machines comprising motor torque offsetseffecting active damping of a driveline operatively connected to theoutput member and motor torque offsets comprising closed-loop motortorque offsets effecting closed-loop correction based upon a differencebetween the monitored state for the input parameter provided by theengine and the target state for the input parameter; transforming themotor torque offsets for the torque generating machines to input andoutput torque offsets to the transmission, said transforming comprisinga linear transformation based on a time rate of change in an input speedof the input member provided by the engine; adjusting operation of theengine based upon the input and output torque offsets to thetransmission; and controlling power flow between the engine, the torquemachines, the energy storage device, and the output member to achievethe output torque command based upon the adjusted operation of theengine.